Investment Securities - Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Fair Value
Less than 12 Months	$ 1,229,529	$ 636,389
12 Months or Longer	305,960	8,829
Total	1,535,489	645,218
Gross Unrealized Losses
Less than 12 Months	82,916	13,239
12 Months or Longer	36,622	401
Total	$ 119,538	$ 13,640
Number of Securities | security	721	161
U.S. Treasury
Fair Value
Less than 12 Months	$ 1,959	$ 999
12 Months or Longer	0	0
Total	1,959	999
Gross Unrealized Losses
Less than 12 Months	5	1
12 Months or Longer	0	0
Total	$ 5	$ 1
Number of Securities | security	2	1
U.S. Government-sponsored agency securities
Fair Value
Less than 12 Months	$ 54,473	$ 68,524
12 Months or Longer	23,869	0
Total	78,342	68,524
Gross Unrealized Losses
Less than 12 Months	3,775	1,545
12 Months or Longer	2,628	0
Total	$ 6,403	$ 1,545
Number of Securities | security	13	8
State and municipal
Fair Value
Less than 12 Months	$ 887,898	$ 138,187
12 Months or Longer	16,888	505
Total	904,786	138,692
Gross Unrealized Losses
Less than 12 Months	62,732	894
12 Months or Longer	2,594	4
Total	$ 65,326	$ 898
Number of Securities | security	585	103
U.S. Government-sponsored mortgage-backed securities
Fair Value
Less than 12 Months	$ 284,223	$ 427,687
12 Months or Longer	265,203	8,324
Total	549,426	436,011
Gross Unrealized Losses
Less than 12 Months	16,380	10,791
12 Months or Longer	31,400	397
Total	$ 47,780	$ 11,188
Number of Securities | security	120	48
Corporate obligations
Fair Value
Less than 12 Months	$ 976	$ 992
12 Months or Longer	0	0
Total	976	992
Gross Unrealized Losses
Less than 12 Months	24	8
12 Months or Longer	0	0
Total	$ 24	$ 8
Number of Securities | security	1	1